There are many types of solid cosmetic sticks that are commercially available or otherwise known in the various arts. These cosmetic sticks include products such as moisturizers, perfumes or fragrances, skin conditioners, antiperspirants, anti-wrinkle products, pharmaceuticals, deodorants, make-up and foundations, sunscreens, and many other products intended for topical application to the skin. Many of these products contain a cosmetic active dispersed within a suitable liquid carrier and contained within a solid gellant or wax matrix that provides the product with sufficient hardness to form a solid stick composition. In addition to providing sufficient product hardness, the solid gellant or wax matrix also acts to contain the liquid carrier and any other liquid ingredients sufficiently to prevent syneresis of such liquids from the product form prior to application.
Wax gellants such as stearyl alcohol and other fatty alcohols are especially common in many commercially available cosmetic stick products. These waxes typically provide a solid matrix within which the cosmetic active and a liquid carrier can be contained with minimal or no liquid syneresis during storage. Other gellants such as the triglyceride gellants have also been used in solid cosmetic sticks, due in large part to the lower raw material cost associated with the use of natural triglycerides.
It has now been found, however, that cosmetic sticks that contain triglyceride gellants can develop stability problems after exposure to high and then low storage temperatures, which can then result in an undesirable softening of and excessive liquid syneresis from the cosmetic stick matrix. It has also been found that triglyceride-based cosmetic stick compositions can be formulated into a more temperature-stable stick form. These compositions are formulated so that exposure to high and then low storage temperatures does not result in excessive softening of the product form and also does not result in excessive development of solvent syneresis during exposure to such temperature changes. It has been found that this can be accomplished by formulating the composition with solid polymorphic triglycerides characterized by beta prime-2 (.beta.'-2) crystalline order within the finished product form. It has been found that by formulating these triglyceride gellants in this manner, that product stability is improved such that product hardness is better maintained and liquid syneresis minimized, especially when exposed to higher and then lower storage temperatures.
It is therefore an object of the present invention to provide a solid cosmetic stick composition that contains a triglyceride gellant and is texture and phase stable when exposed to high and then lower storage temperatures. It is a further object of the present invention to formulate such a composition containing a thermodynamically stable triglyceride gellant, one that is characterized by .beta.'-2 crystalline order within the finished product form.